US3805161A - Apparatus for sensing speed - Google Patents

Apparatus for sensing speed Download PDF

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Publication number
US3805161A
US3805161A US00271158A US27115872A US3805161A US 3805161 A US3805161 A US 3805161A US 00271158 A US00271158 A US 00271158A US 27115872 A US27115872 A US 27115872A US 3805161 A US3805161 A US 3805161A
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United States
Prior art keywords
speed
vehicle
responsive
coil
magnet
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00271158A
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English (en)
Inventor
W Bayha
W Grozinger
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Moto Meter GmbH
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Moto Meter GmbH
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Publication date
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P1/00—Details of instruments
    • G01P1/07—Indicating devices, e.g. for remote indication
    • G01P1/08—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers
    • G01P1/10—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers for indicating predetermined speeds
    • G01P1/103—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers for indicating predetermined speeds by comparing the value of the measured signal with one or several reference values
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/42—Devices characterised by the use of electric or magnetic means
    • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
    • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
    • G01P3/4802—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage by using electronic circuits in general
    • G01P3/4805—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage by using electronic circuits in general by using circuits for the electrical integration of the generated pulses
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/42—Devices characterised by the use of electric or magnetic means
    • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
    • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
    • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
    • G01P3/487—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals delivered by rotating magnets

Definitions

  • An apparatus for sensing speed levels of a motor vehicle includes a rotatable magnet, preferably in the shape of a disc.
  • a speedometer drive is arranged to rotate the magnet at an angular velocity related directly to the speed of the vehicle.
  • a coil is positioned in the vicinity of the magnet and is operatively responsive to its magnetic field and thus produces an alternating voltage signal having a frequency related to the speed of the vehicle.
  • a signal processing circuit is coupled to the coil and produces an output signal indicative of the speed of the vehicle in response to the alternating voltage signal received from the coil.
  • the rotatable magnet and the speedometer drive may be parts of a conventional eddy current speedometer.
  • the opaque body or flag enters into the path of a light beam whenever a given speed level is reached so that the light beam is interrupted, thus providing an output signal. It is also possible to provide an apparatus for sensing speed which includes a so-called makeand-break oscillator and a radially extendable body or flag connected to the indicator shaft, the radially extendable body or flag being operatively arranged to move into the resonant coil of the oscillator whenever a given speed level is reached.
  • a further example for sensing the speed of a motor vehicle is a conventional mechanically acting centrifugal pendulum.
  • a knob by twisting a knob, to set a certain vehicle speed level, for example when he desires to drive no more than a certain speed or when there is a general speed limit for extended distances. If this speed limit is reached or exceeded, respectively, a signal could be produced, previously determined functions and operations at other speed levels not being thereby influenced.
  • An object of the present invention is to provide an apparatus for sensing speed levels of motor vehicles having a speedometer, which apparatus operates with high precision.
  • An additional object of the present invention is to provide an apparatus for sensing speed levels of motor vehicles which is able to process a plurality, preferably any desired number, of sensed speed levels into respective output signals and to display them separately.
  • a further object of the present invention is to provide an apparatus for sensing speed levels of motor vehicles which can be installed in virtually any motor vehicle with little additional expense, no tampering with the engine, the gear assembly or other drive assemblies being necessary.
  • a speedometer drive is coupled to the magnet for rotating the magnet at an angular velocity related to the speed of the vehicle.
  • a coil is positioned in the vicinity of the magnet and responds to the magnetic field of the magnet for producing an alternating voltage signal having a frequency related to the speed of the vehicle.
  • a signal processing circuit is coupled to the coil and produces an output signal indicative of the speed of the vehicle in response to the alter nating voltage signal from the coil.
  • the rotating generator magnet of the speedometer is driven via the speedometer shaft.
  • a receiver coil is disposed in the vicinity of the rotating magnet.
  • an alternating output voltage is produced which is fed from the receiver coil to a processing circuit.
  • the zero passages or frequency of the alternating voltage produced in the receiver coil are a measure for the speed of the vehicle.
  • the speedometer shaft moves in absolute proportionality to the rotation of the rear axle, it is assured that the measuring results do not include measuring errors inherent in the system and in conventional speedometers.
  • the revolutions of the speedometer shaft may be utilized in a digital manner due to the field developed by the rotating generator magnet of the speedometer. lnaccuracies and errors known to exist in conventional spring restrained speedometers, in which eddy currents induced by an aluminum disc produce a speed indication signal, are avoided.
  • the receiver coil is positioned about a shortcircuit ring made of magnetizable material enclosing the rotating generator magnet, the ring providing a magnetic short circuit. No modifications to the speedometer itself are required. The apparatus of the present invention does not interfere with the operation of the speedometer itself.
  • a further substantial advantage of the present invention is that the accuracy of the speed indication is not altered in any way by aging; even when the conventional speedometer indication becomes more and more inaccurate, the signal production at the given speed levels is effected with unchanging precision at the intended speed levels since aging of the magnet and displacement of the components with respect to one another, as well as temperature influences, can exert no influence whatsoever on the frequency or zero passages of the output voltage signals produced in the receiver coil.
  • FIG. 1 is an exploded perspective view of the lower portion of an automobile speedometer modified in accordance with the present invention
  • FIG. 2 is a top view of the lower portion of the speedometer shown in FIG. 1.
  • FIG. 3 is a schematic diagram of a signal processing circuit for evaluating signals produced by the apparatus shown in FIGS. 1 and 2.
  • a modified, commercially available speedometer for a motor vehicle includes a conventional housing 1, a conventional rotatable generator magnet 4 and a conventional aluminum disc 2 in the form of a hood which covers the magnet 4, the aluminum disc 2 being shown detached for purposes of clarity.
  • the conventional upper portion of the speedometer with its indicating scale has not been shown in FIGS. 1 and 2 and is not required for the further explanation.
  • a lower portion 3 of the housing 1 holds a conventional speedometer shaft (not visible) whose revolution effects directly a rotation of a generator magnet 4, i.e., the magnet 4 which is a permanent magnet rotates at a speed which is directly proportional to the speed of the vehicle and constitutes a highly accurate representation of this vehicle speed. Measuring errors cannot occur at this stage.
  • the permanent magnet 4 which is provided in the form of a rotatable disc has two north and two south poles.
  • the magnet 4 is covered by the hood-shaped disc 2 preferably made of aluminum. Upon rotation, the magnetic field of the permanent magnet 4 induces eddy currents in the aluminum 'disc 2 which cause the aluminum disc 2 to follow in the direction of rotation of the magnetic field.
  • the aluminum disc 2 is restrained by the spring force of a helical spring (not visible) connected to its shaft 2' so that its maximum possible angle of rotation, which is substantially proportional to the speed of rotation of the permanent magnet 4, constitutes a measure for the speed of the vehicle.
  • the thus obtained speed indication is not very precise, and may be subject in its accuracy to temperature fluctuations and aging so that a derivation of measured values from the angle of rotation of the aluminum disc 2'becomes faulty.
  • a receiver coil 5 is disposed in the vicinity of the permanent magnet 4 driven by the speedometer shaft.
  • the coil 5 only need be operatively positioned in such a way that it is periodically intersected by the magnetic field originating from the rotating permanent magnet 4.
  • the coil5 is wound about a short-circuit ring 6 made of a magnetic material as a single or multiple layer winding.
  • the short-circuit ring 6 provides a low reluctance path for the flux emanating from the disc-shaped permanent magnet 4, as illustrated in FIG. 2. In this manner it is assured that the coil 5 is always intersected by the magnetic flux and an induced output voltage signal is produced in the coil 5 upon rotation of the permanent magnet 4, the output voltage signal being fed to the signal processing circuit shown in FIG. 3. 7
  • a weakening or fluctuation of the magnetic field produced by the permanent magnet 4 or other changes in the structural components of the speedometer drive can affect the output voltage signal produced in the coil 5 as far as the amplitude of this voltage signal is concerned, but the zero passages or frequency of this voltage signal precisely depend on the rotation of the permanent magnet 4 and are only a measure of this rotation.
  • the construction of a conventional speedometer is modified in accordance with the present invention by positioning the receiver coil 5 about the magnetic short-circuit ring 6, which usually encloses the permanent magnet 4 required to drive the speedometer indicator, during manufacture, in such a manner that the coil 5 is intersected by the lines of force of the pennanent magnet 4.
  • Electrodes to the ends of the coil 5 are provided by a pair of output terminals or leads 7a and 7b which can be attached tothe ends of the coil 5 during assembly or may be constituted by extensions of the wire forming the coil 5.
  • the leads 7a and 7b are brought out from the housing 1 via a suitably arranged aperture. A change in the speedometer characteristic per se does not result from the installation of the additional coil 5 and it is not necessary to change the original dimensions of the speedometer since the coil can be kept sufficiently small.
  • the signal to be obtained at the output terminals or leads 7a and 7b from the coil 5 is an approximate sine oscillation in the illustrated embodiment.
  • This signal is fed to the evaluation circuit shown in FIG. 3 for further processing.
  • the receiver coil 5 (FIGS. 1 and 2) corresponds to the coil 5 shown in FIG. 3.
  • the diode 8 becomes respectively conductive or blocks so that voltage variations appear at the base terminal of a transistor 9 which voltage variations are amplified by the transistor 9 and appear as amplified pulses at its collector.
  • These amplified pulses are fed to a subsequently connected transistor amplifier 10.
  • the first transistor 9 acts as a pulse preamplifier and comprises stage I of the signal processing circuit.
  • Stage II is formed by the transistor amplifier 10 which operates somewhat in the manner of a simplified mo'nostable multivibrator.
  • the pulses produced at its collector are differentiated by the RC network 11 and 12 of a subsequent stage 111 and the resulting negative going spike pulses are simultaneously conducted to ground via a diode 13.
  • the positive going spike pulses travel via a diode 14 to a charging and smoothing filter which includes capacitors 15, 16, and 17, and resistors 18 and 19 which constitute stage IV of the processing circuit.
  • the capacitors 15, 16, and 17 whose one terminal is connected to ground, shown as negative, and whose other terminals are connected to the respective connecting points of the series circuit formed by the two resistors 18 and 19, have capacitance values from about 1 ,if to about t, so that the capacitors can charge to a certain positive charge level in dependence on the speed of rotation of the permanent magnet 4 (FIGS. 1 and 2) and thus in dependence on the number of incoming pulses supplied from the transistor amplitier 10.
  • the stage IV acts as an integrator.
  • a resistor 21 provides a continuous discharging path for the integrating filter formed by the stage IV.
  • a diode 20 is connected in series with the resistor 21 and the capacitor 17 and serves to improve the temperature characteristic of the processing circuit.
  • a positive voltage is produced at a point 22 of the circuit which is precisely dependent on the speed of the driven vehicle, i.e. on the number of pulses produced by the transistor amplifier 10.
  • a transition from digital to analog evaluation takes place between the stages III and IV, the digital signals arriving as positive going voltage spikes and being summed in the smoothing filter of stage IV operating as a summing or integrating member.
  • the voltage level at the point 22 can be determined via subsequently connected measuring arrangements.
  • Respective signal inputs of integrated Schmitt trigger circuits 23, 24 and, if desired, additional Schmitt trigger circuits such as a circuit 25 are each coupled to the'point 22.
  • Schmitt trigger circuits are employed since thus it is possible to set a very low hysteresis.
  • the integrated components acting respectively as each of the Schmitt trigger circuits 23, 24, and 25 have two inputs.
  • the potential of one input 26a of the Schmitt trigger circuit 23 and one input 26b of the Schmitt trigger circuit 24 are precisely set and given by respective voltage divider circuits formed respectively by resistors 27, 28, 29, and and resistors 27', 28', 29', and 30. It is to be understood that one input of each additional Schmitt trigger circuit, such as the circuit 25, is to be connected to similar voltage dividers.
  • the corresponding Schmitt trigger circuit 23 or 24 flips to its other state and thus applies full voltage to a subsequently connected relay 32a or 32b, respectively, so that the associated relay is energized and, in turn, enables further circuits (not shown) to produce signals or itself effects the necessary switchings such as the lighting of a signalling light or the sounding of an alarm.
  • the relays 32a and 32b are connected, respectively, in parallel with diodes in a known manner to limit the cut-off voltage. Since the inputs of the integrated Schmitt trigger circuits 23, 24, 25, etc. practically place no load on point 22 of the circuit, it
  • any desired number of subsequently connected Schmitt trigger circuits or other similarvcircuit arrangements which can be set to any desired voltage by the appropriate setting of the resistors 29 or 29', which are preferably variable as shown, or similar resistors in the voltage divider circuits.
  • any desired speed level indicating or switching circuits can be provided and be made independently and individually settable. It is possible, for example, to switch the Schmitt trigger circuit 23 at the speed of 30 miles per hour, the circuit being able to react with such sensitivity that the switching takes place precisely at the given speed and a signal is produced from the Schmitt trigger circuit 23.
  • variable resistor 29 for biasing the first Schmitt trigger circuit 23 a specially calibrated potentiometer may be employed which can be set, for example, via a button accessible from the dashboard, on a scale calibrated in miles per hour. Then it is possible for every driver to set a given speed according to his desire by electronic means at which, for example, a lamp will light up. Such a signal can also be used, in a further embodiment of the present invention, to actuate the accelerator and/or the brake of avehicle.
  • Schmitt trigger circuits If a further one of the Schmitt trigger circuits is also made variable, then it is possible to set a certain speed interval which is to be maintained, where the circuits can be set in such a way that a certain lamp lights up when the set speed interval is being maintained. This contributes to uniform traffic flow.
  • An apparatus for sensing speed levels of a motor vehicle having an eddy current speedometer which includes rotatable magnet means driven by a speedometer drive means, the apparatus comprising coil means positioned in the vicinity of said magnet means and responsive to its magnetic field for producing an alternating voltage signal having a frequency related to the speed of the vehicle, and signal processing circuit means coupled to said coil means and responsive to the alternating voltage signal for producing an output signal indicative of the speed of the vehicle, said signal processing circuit means including:
  • a. pulse-forming amplifier means coupled to said coil means and responsive to the alternating voltage signal for producing pulses
  • integrating filter means coupled to'said differentiating means and responsive to the spike pulses of given polarity for producing the direct voltage output signal indicative of the speed of the vehicle, said integrating means having first resistive means, capacitive means and second resistive means for constantly discharging said capacitive means, wherein the voltage state of said integrating means is a measure of the repetition rate of the pulses of given polarity and thus the speed of the vehicle;
  • At least one bias voltage supply means having a respective voltage divider means having at least two series connected resistors, wherein one of said two series connected resistors in said voltage divider is adjustable and is calibrated in units of distance per time period and is operatively arranged to be selectively adjusted from the dashboard of the vehicle;
  • said magnet means comprises a disc-shaped permanent magnet and the apparatus further comprises a magnetic short-circuit ring positioned about the periphery of said disc-shaped permanent magnet, said coil means being disposed about said ring.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)
  • Linear Or Angular Velocity Measurement And Their Indicating Devices (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Measurement Of Distances Traversed On The Ground (AREA)
US00271158A 1971-07-17 1972-07-12 Apparatus for sensing speed Expired - Lifetime US3805161A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2135912A DE2135912A1 (de) 1971-07-17 1971-07-17 Vorrichtung zur abtastung von geschwindigkeitswerten bei kraftfahrzeugen

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US3805161A true US3805161A (en) 1974-04-16

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US00271158A Expired - Lifetime US3805161A (en) 1971-07-17 1972-07-12 Apparatus for sensing speed

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US (1) US3805161A (enrdf_load_html_response)
JP (1) JPS4829123A (enrdf_load_html_response)
DE (1) DE2135912A1 (enrdf_load_html_response)
FR (1) FR2146267B1 (enrdf_load_html_response)
GB (1) GB1327559A (enrdf_load_html_response)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2657436A1 (de) * 1975-12-29 1977-07-07 Elliott Brothers London Ltd Automatische niederfrequenz-geraeuschsperr-anordnungen
US4083423A (en) * 1975-07-02 1978-04-11 Dana Corporation Vehicle road speed signal source
FR2405595A1 (fr) * 1977-10-04 1979-05-04 Synchro Start Products Commutateur de commande de vitesse de precision
US4168516A (en) * 1976-11-26 1979-09-18 Synchro-Start Products, Inc. Precision speed switch control
US4248082A (en) * 1978-12-28 1981-02-03 Farmer D Eugene Anemometer
EP0037657A1 (en) * 1980-04-04 1981-10-14 Toyota Jidosha Kabushiki Kaisha A rotating speed detecting device of a rotary type electrostatic spray painting device
DE3124700A1 (de) * 1981-06-24 1983-01-13 Robert Bosch Gmbh, 7000 Stuttgart "einrichtung zur erfassung der drehzahl von rotierenden teilen, insbesondere nach dem wirbelstrommessverfahren"
US4376915A (en) * 1981-03-30 1983-03-15 Dart Controls, Inc. Tachometer
US4406983A (en) * 1981-12-29 1983-09-27 International Business Machines Corporation Rotational magnetic transducer
US4488198A (en) * 1981-01-15 1984-12-11 Sundstrand Corporation Protective circuit for clutchless parallel generating system
US5152544A (en) * 1989-12-20 1992-10-06 Eaton Corporation Articulation angle sensor
US5448920A (en) * 1991-01-15 1995-09-12 Ketelsen; Broder Device for inductively measuring the state of a stream of electrically conductive liquid
US5523680A (en) * 1993-06-15 1996-06-04 Toyota Jidosha Kabushiki Kaisha Wheel speed sensor that accurately senses variations in magnetic reluctance
US5742160A (en) * 1993-01-15 1998-04-21 Hughes Electronics Apparatus for determining angular position and rotational speed using a rotating magnet and a directional magnetometer
US6333687B1 (en) 1995-05-04 2001-12-25 Labelle Paul J. Automatic underspeed warning system
US7411388B2 (en) * 2005-08-30 2008-08-12 Baker Hughes Incorporated Rotary position sensor and method for determining a position of a rotating body
US20120230839A1 (en) * 2011-03-11 2012-09-13 Nidec Motor Corporation Hvac blower motor with speed sensor

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT331355B (de) * 1974-10-09 1976-08-25 Philips Nv Vorrichtung zur gewinnung einer impulsfolge in abhangigkeit von der drehzahl eines rotierenden systems
GB2197108A (en) * 1986-11-05 1988-05-11 Pamax Nominees Pty Ltd Speed limit alarm for motor vehicle

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3505879A (en) * 1968-07-31 1970-04-14 Ford Motor Co Electrical generator including components of an automotive vehicle mechanical speedometer
US3548663A (en) * 1968-07-31 1970-12-22 Ford Motor Co Electrical generator including components of an automotive vehicle mechanical speedometer
US3560854A (en) * 1967-10-16 1971-02-02 John I Moss Inc Pulse actuated speed responsive system
US3573619A (en) * 1969-02-10 1971-04-06 Motorola Inc Electromagnetic system for scaling frequencies which are proportional to the angular velocities of selected rotating shafts
US3704445A (en) * 1971-07-20 1972-11-28 Richard R Lanham Digital read out indicator for vehicles

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3560854A (en) * 1967-10-16 1971-02-02 John I Moss Inc Pulse actuated speed responsive system
US3505879A (en) * 1968-07-31 1970-04-14 Ford Motor Co Electrical generator including components of an automotive vehicle mechanical speedometer
US3548663A (en) * 1968-07-31 1970-12-22 Ford Motor Co Electrical generator including components of an automotive vehicle mechanical speedometer
US3573619A (en) * 1969-02-10 1971-04-06 Motorola Inc Electromagnetic system for scaling frequencies which are proportional to the angular velocities of selected rotating shafts
US3704445A (en) * 1971-07-20 1972-11-28 Richard R Lanham Digital read out indicator for vehicles

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4083423A (en) * 1975-07-02 1978-04-11 Dana Corporation Vehicle road speed signal source
DE2657436A1 (de) * 1975-12-29 1977-07-07 Elliott Brothers London Ltd Automatische niederfrequenz-geraeuschsperr-anordnungen
US4168516A (en) * 1976-11-26 1979-09-18 Synchro-Start Products, Inc. Precision speed switch control
FR2405595A1 (fr) * 1977-10-04 1979-05-04 Synchro Start Products Commutateur de commande de vitesse de precision
US4248082A (en) * 1978-12-28 1981-02-03 Farmer D Eugene Anemometer
EP0037657A1 (en) * 1980-04-04 1981-10-14 Toyota Jidosha Kabushiki Kaisha A rotating speed detecting device of a rotary type electrostatic spray painting device
US4488198A (en) * 1981-01-15 1984-12-11 Sundstrand Corporation Protective circuit for clutchless parallel generating system
US4376915A (en) * 1981-03-30 1983-03-15 Dart Controls, Inc. Tachometer
DE3124700A1 (de) * 1981-06-24 1983-01-13 Robert Bosch Gmbh, 7000 Stuttgart "einrichtung zur erfassung der drehzahl von rotierenden teilen, insbesondere nach dem wirbelstrommessverfahren"
US4406983A (en) * 1981-12-29 1983-09-27 International Business Machines Corporation Rotational magnetic transducer
US5152544A (en) * 1989-12-20 1992-10-06 Eaton Corporation Articulation angle sensor
US5448920A (en) * 1991-01-15 1995-09-12 Ketelsen; Broder Device for inductively measuring the state of a stream of electrically conductive liquid
US5742160A (en) * 1993-01-15 1998-04-21 Hughes Electronics Apparatus for determining angular position and rotational speed using a rotating magnet and a directional magnetometer
US5523680A (en) * 1993-06-15 1996-06-04 Toyota Jidosha Kabushiki Kaisha Wheel speed sensor that accurately senses variations in magnetic reluctance
US6333687B1 (en) 1995-05-04 2001-12-25 Labelle Paul J. Automatic underspeed warning system
US7411388B2 (en) * 2005-08-30 2008-08-12 Baker Hughes Incorporated Rotary position sensor and method for determining a position of a rotating body
US20120230839A1 (en) * 2011-03-11 2012-09-13 Nidec Motor Corporation Hvac blower motor with speed sensor
US9388819B2 (en) * 2011-03-11 2016-07-12 Nidec Motor Corporation HVAC blower motor with speed sensor

Also Published As

Publication number Publication date
DE2135912A1 (de) 1973-03-22
FR2146267B1 (enrdf_load_html_response) 1975-10-03
JPS4829123A (enrdf_load_html_response) 1973-04-18
GB1327559A (en) 1973-08-22
FR2146267A1 (enrdf_load_html_response) 1973-03-02

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